On my side I have FreeIPA for LDAP/Kerberos/DNS/Certificate and Authentik for SSO (pulling account info from FreeIPA). I am pretty satisfied with FreeIPA in general. I even use FreeIPA with DDNS and create some domain for kubernetes directly. I also added freeipa as a Certificate Issuer in Cert-manager which allow me to generate internal certificate for my ingress.

Here are some of my notes.

You need to have a hostname set up on the server:

hostnamectl set-hostname your-server.domain.internal

You will need an entry in /etc/hosts defining the IP of the service with the hostname.

vi /etc/hosts

10.0.0.10 your-server.domain.internal

mkdir /opt/freeipa

docker run --sysctl net.ipv6.conf.all.disable_ipv6=0 --name $(hostname -s) -ti -h $(hostname -f) --read-only -v /opt/freeipa:/data -e IPA_SERVER_IP=$(ip a show dev ens18 | grep inet | awk '{ print $2 }' | sed -s 's//.*$//') freeipa/freeipa-server:rocky-9 ipa-server-install -r DOMAIN.INTERNAL -n domain.internal --no-ntp --setup-dns --forwarder=1.0.0.1 --forwarder=1.1.1.1 --reverse-zone=10.in-addr.arpa. --ip-address=$(ip a show dev ens18 | grep inet | awk '{ print $2 }' | sed -s 's//.*$//')

Here some stuff you might need to edit in the docker command:

Server IP:

-e IPA_SERVER_IP=$(ip a show dev ens18 | grep inet | awk '{ print $2 }' | sed -s 's/\/.*$//') #This line use ens18 (default for proxmox) to get the ip and use it to host the service. Change it to the IP you want for the freeipa server, same for --ip-address=

IPV6 usage:--sysctl net.ipv6.conf.all.disable_ipv6=0 # I didn't wanted to use ipv6 in my lab so you can switch it to 1 if you want ipv6 enabled

Realm domain:

-r DOMAIN.INTERNAL # Change this to whatever realm domain you want ALWAYS UPPERCASE

Domain name:

-n domain.internal # The LDAP domain to use, usually it is the realm name in lowercase

DNS parameter:

--forwarder=1.0.0.1 #These are cloudflare public dns

--forwarder=1.1.1.1 #These are cloudflare public dns

--reverse-zone=10.in-addr.arpa. #This is the reverse zone for the domain server

I propose you to try Freeipa in a docker container on one of your ubuntu server. It gives all functionality you requested and it is very easy to use. Biggest downside is that Freeipa create a Trust Authority certificate issuer and all users/computer using your internal domain will need to install the Authority Certificate to not get an error when validating personal certificate. Apart from that it is working very well.